Closed flow caloric test method

ABSTRACT

A method of caloric vestibular testing comprises inserting an inflatable receptacle into an ear canal; admitting pressurized calorized fluid into the receptacle to cause its expansion laterally within the ear canal and longitudinally up to the tympanic membrane, such expansion filling the cross-sectional area of at least a portion of the ear canal; while inflating the receptacle, venting air trapped between the receptacle and the tympanic membrane to atmosphere; and circulating a volume of calorized liquid through the receptacle while carrying out a caloric vestibular function testing procedure.

This application is a continuation of application Ser. No. 771,340,filed Feb. 23, 1977, now abandoned, which was a continuation-in-part ofapplication Ser. No. 734,291, filed Oct. 21, 1976, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a method for caloric nystagmus testing.More particularly, the present invention relates to improvements whichsimplify the inducing of nystagmus and greatly expand the practicalutility of caloric nystagmus testing.

Nystagmus is a regular, alternating eye movement of variable velocitywhich can be induced by many known methods. It is well-recognized thatby monitoring controllably-induced nystagmus a diagnostician canascertain various vestibular disorders as well as other isolatedclinical pathology as may pertain to various medico-surgicalsubspecialties. Measurement of nystagmus can be done visually or byelectronic apparatus, either of which may be employed in conjunctionwith the present invention.

Caloric nystagmus testing involves the injection of specified fluidvolumes at known temperatures into the patient's ear to induce anystagmus response. The most widely used fluid for caloric testing iswater. However, water necessarily overflows the patient's ear, isuncomfortable for the patient, is messy to handle, and requires muchmaintenance. Further large amounts of water are required, all of whichmust be heated from ambient temperature to specific temperatures aboveambient. Air has also been used as a caloric test fluid but often causesundue patient discomfort; furthermore, variability of test results havebeen observed due in part to the lower heat capacity of air andsensitivity to applicator positioning. Open (i.e. overflowing) watercaloric testing is medically contraindicated for patients having: a holein the ear drum; an ear infection; a prior surgically-created cavity inthe ear; or middle ear ventilating tubes.

It is an object of the present invention to provide a method forconducting caloric tests without the aforementioned disadvantages.

It is another object of the present invention to provide a method forconducting caloric tests without requiring injection of fluid directlyinto the ear.

It is still another object of the present invention to provide a methodof conducting caloric nystagmus tests without flowing air or waterdirectly into the patient's ear.

It is still another object of the present invention to provide anenergy-conserving technique for inducing nystagmus, saving on both waterand heating consumption.

There has been some suggestion in the prior art that caloric testing canbe performed by the finger-cot method whereby a balloon-like member isinserted in the ear and the test liquid is caused to flow into thatmember. In practice, however, it has been found that introduction of theballoon-like member into the ear is extremely difficult; moreover, themeasurement has proven highly insensitive and many of the disadvantagesof direct flow into the ear (mess, undue pressure build-up, etc.)remain. Further, there is a danger that the finger-cot, when expanded,will be too deep within the ear canal, resulting in damage to thetympanic membrane from pressure build-up.

It is a further object of the present invention to provide a method forperforming caloric nystagmus tests without the need for directly flowingtest fluid into the ear and without the disadvantages of the finger-cotapproach.

SUMMARY OF THE INVENTION

In accordance with the present invention a probe or receptacle, whichprovides an internal flow path for caloric test fluid, is provided. Theprobe is made of extremely thin, durable and flexible material capableof efficiently transferring thermal energy from test fluid in the probeto the patient's ear canal and tympanic membrane. In one embodiment theprobe is semi-rigid, to facilitate insertion into the ear canal, and isof predetermined length to assure that it does not rupture the tympanicmembrane when expanded under the pressure of test fluid to conform tothe canal. If desired, the forward end of the probe may be contoured tomatch the tympanic membrane. It is also possible to provideflowdirecting vanes internally of the probe to establish a desired flowpath for test fluid.

In other embodiments an ear mold is provided and contoured to match thetragus region of the ear, which region is a key anatomical landmark fordepth insertion into the ear canal. The ear mold may be considered astop member and has a distensible, inflatable balloon-like memberattached to its forward end, the balloon-like member preferably beingdeflated during insertion of the probe. The ear mold establishes astandard insertion depth and has inflow and outflow passages for testfluid defined therethrough. The balloon-like member serves as areceptacle for test fluid and when inflated by the test fluid it expandsto the contour of the ear canal and effects nystagmus inducing thermaltransfer. An air vent passage is provided through the balloon and earmold to permit evacuation of air trapped in the ear between theexpanding balloon and the ear drum; the hermetically-sealing ear moldrenders this vent passage particularly important. The balloon member, aswell as the vent passage, can be corrugated at least in part, and adepth indicator can be provided. The inlet to the vent is inwardlyconically shaped to prevent injury or irritation to the tympanicmembrane, and plural inlets can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of one specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a side view in section of one embodiment of the probe of thepresent invention;

FIG. 2 is a view in section taken along lines 2--2 of FIG. 1;

FIG. 3 is a view in section taken along lines 3--3 of FIG. 1;

FIG. 4 is a side view in section of another embodiment of the presentinvention;

FIG. 5 is a view in section taken along lines 5--5 of FIG. 4;

FIG. 6 is an end view in plan of still another embodiment of the presentinvention;

FIG. 7 is a view in section taken along lines 7--7 of FIG. 6;

FIG. 8 is a side view in section of still another embodiment of thepresent invention shown in partially expanded state;

FIG. 9 is a side view in section of the embodiment of FIG. 8 shown inpartially collapsed state; and

FIG. 10 is a side view in section of still another embodiment of thepresent invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring specifically to the drawings, a generally cylindrical probe orreceptacle assembly 10 comprising one form of the present invention isproportioned to permit insertion of its distal end area (to the right asillustrated) into a patient's ear along the longitudinal dimension ofthe probe. The probe has a semi-rigid, hollow portion defined by outerwall 11, of generally cylindrical configuration, which is contoured atits distal end surface 12 to generally match the contour of the tympanicmembrane of the human ear. More specifically, the distal end surface 12is sloped so that its bottom portion projects beyond its top portion, asillustrated. The outer wall 11 is shown in its inflated, distendedposition in FIG. 1, but normally would be somewhat smaller in itsrelaxed state.

The opposite or proximal end 13 of the probe is generally circular andhas a test fluid inlet opening 14 and a test fluid outlet opening 15defined therein. Inlet opening 14 is defined in the top semi-circle ofend surface 13 and communicates with an inlet flow tube 16. Outletopening 15 is disposed in the bottom semi-circle of end surface 13 andcommunicates with an outlet flow tube 17.

A generally coaxial interior wall 18 of the probe is also of generallycylindrical configuration and is substantially equidistant from outerwall 11 at all points along its length. In addition, wall 18 has an endportion 19 which is similarly spaced from end surface 12 of the outerwall 11.

The annular space between walls 11 and 18 is divided into upper andlower halves 21 and 22, respectively, by flat, longitudinally-extendinghorizontal vanes 24 and 25 that serve to guide incoming test fluid tothe distal end of receptacle 10. Upper half 21 communicates with inlettube 16 via inlet opening 14 and comprises a fluid inflow path withinthe probe 10. Lower half 22 communicates with outflow tube 17 via outletopening 15 and comprises a fluid outflow path within the probe 10. Aplurality of struts 23 are secured between walls 11 and 18 at variouslocations.

In performing a caloric nystagmus test with probe 10, calorized inletfluid at the desired temperature is caused to flow into the probe viainlet tube 16. The fluid is preferably a liquid, because it has greaterheat transfer characteristics than a gas, and may be water. Theinflowing liquid flows in through the upper half 21 of probe 10, betweenthe ends 12 and 19 of walls 11 and 18, respectively, and out through thelower half 22 of the probe and outlet tube 17. When the probe isproperly inserted in a patient's ear and inflated with end surface 12against the patient's tympanic membrane, efficient thermal transferbetween the flowing fluid and the tympanic membrane takes place throughouter wall 11. This thermal transfer induces the nystagmus responsewhich can be monitored by any available apparatus or technique.

The pressure of the flowing fluid tends to expand outer wall 11 to morereadily match the contour of the external auditory canal and tympanicmembrane, thereby providing for more efficient thermal transfer betweenthe fluid and the ear. The pressure of the fluid also tends to separatethe walls 11 and 18, which separation is restrained by struts 23.

It is important that the material employed in the probe be extremelythin to permit efficient thermal transfer between the fluid and thetympanic membrane and ear canal. In addition the material must bedurable, to prevent rupture, and flexible, to permit optimum conformanceto the ear surface when the pressurized test liquid is flowing throughthe probe. Moreover, the material must be semi-rigid; that is, it musthave sufficient rigidity to permit easy insertion of the probe into thepatient's ear. Certain types of polyurethane or silicone rubber are wellsuited to provide these characteristics. By way of example only, asegmented polyether polyurethane product sold by Ethicon, Inc., ofSomerville, New Jersey, under the trademark BIOMER, is suitable for usein probe 10, particularly in the thicknesses of approximately 0.125 mm.Likewise, a silicone elastomer suitable for use at a thickness ofapproximately 0.125 mm. (or special thinner formulations) is marketed byDow Corning Corporation of Midland, Michigan, under the trademarkSILASTIC. Various other materials are suitable as will be appreciated bythose skilled in this field.

The tubes 16 and 17 can be made of any flexible material which readilybonds to the probe material and which is not adversely affected by thetest liquid. The tubes may be color-coded, if desired, or otherwisemarked to distinguish the upper or inlet tube 16 from the lower oroutlet tube 17. This assures proper orientation of the probe so thatsurface 12 abuts the tympanic membrane.

The dimensions of the probe depend upon whether it is intended for usein an average-sized adult's ear or a child's ear. By example only,typical dimensions for adult use are as follows:

    ______________________________________                                        A (inner diameter of                                                                           3 mm                                                         cylindrical wall 18)                                                          B (outer diameter of probe)                                                                    6 mm                                                         C (length of probe)                                                                            32 mm                                                        Thickness of walls 11, 18                                                                      0.025 to 0.25 mm                                             Length of tubes 16, 17                                                                         approximately 30 mm (as needed)                              ______________________________________                                    

Another embodiment of the present invention is probe or receptacleassembly 30 illustrated in FIGS. 4 and 5. Probe assembly 30 includes anelongated balloon-like member 31 having a distal area termination inclosed end 32 and a proximal end 33 at the proximal area of the assembly30. Member 31 is preferably fabricated from the same type of plasticmaterial described above for probe 10; however, because of the absenceof internal struts 23 or equivalent, member 31 is collapsible when notinflated by test fluid. The proximal end 33 of member 31, in thisembodiment is secured (by means of adhesive material, thermal orchemical bonding, etc.) to the distal concave end of an ear mold 34.Alternatively, balloon-like member 31 and ear mold 34 may be formed aspart of the same molded piece. The ear mold 34 preferably has someflexibility but in any case has sufficient rigidity to be inserted intoand hermetically seal a patient's ear. For this purpose the ear mold 34is contoured to match the walls of the outer portion of thecartilagenous auditory canal. (It will be appreciated that differentsize ear molds may be used for children and adults.) The ear mold widensat its proximal end 50 to limit the extent to which member 31 and thedistal end of the ear mold can enter an ear canal.

When fully expanded, member 31 is of generally cylindrical configurationwith ends 32 and 33 rounded. A generally conical or funnel-shapedinwardly convergent recess 35 is defined in member 31 centrally offorward end 32 where duct 36 and member 31 meet with each other. Recess35 communicates at its narrow end with a flexible air tube 36 extendinglongitudinally from recess 35 through member 31 to a hole 37 defined inend 33, the tube 36 defining a separate fluid flowpath from the testfluid inlet and outlet. Tube 36 may be accordian-pleated or corrugatedas described in relation to FIGS. 8, 9 and 10, below; importantly, tube30 must have sufficient radial strength to prevent it from collapsingwhen member 31 is pressurized with test liquid. The air tube 36 isconfined within the external boundaries of balloon 31 to prevent anyprojections from contacting the tympanic membrane. The conical inlet orrecess 35 likewise prevents irritation to the membrane and prevents theinlet from sealing up while the balloon is expanding within the earcanal and towards the tympanic membrane. A bore 38, extendinglongitudinally through ear mold 34, communicates with air tube 36 athole 37. A fluid inlet tube 39 extends through another bore 40 definedthrough ear mold 34 to provide a flow path for test fluid intoballoon-like member 31 from beyond the proximal end 50 of the ear mold.A fluid outlet tube 41 extends through still another bore 42 definedthrough ear mold 34 to provide a flow path for test fluid out ofballoon-like member 31 to beyond the proximal end 50 of the ear mold.

It should be noted that the test fluid inlet and outlet tubes need notbe integral parts of the balloon-like member 31 as shown; rather, theymay be separate tubes which can be inserted part way into bores 40 and42 to communicate via these bores with suitably provided holes in theproximal end 33 of member 31. Similarly, air tube 36, rather thanterminating at the proximal end 33 of member 31, may extend into orbeyond the ear mold through bore 38.

A depth indicator 43 for indicating the extension of end 32 relative tothe proximal end of probe assembly 30 takes the form of a flexible wireor string which is secured to the distal end area of air tube 36 or thenarrow end of conical recess 35 and extends through that tube outthrough bore 38 in ear mold 34. Depth indicator 43 is color-coded orotherwise indexed so that as the balloon-like member 31 expands in apatient's ear, movement of the indices on indicator 43 into bore 38render the expansion noticeable outside the ear. A particular indexmark, when located at the entrance to bore 38, signifies full expansionof member 31.

When probe 30 is not in use it may be stored compactly with member 31,with tube 36 collapsed into the concave forward end of the ear mold 34.To this end, indicator 43 serves as a pull mechanism or drawstring topositively effect collapse when pulled through bore 38. Alternatively,if air tube 36 is made semi-rigid so as not to be fully collapsible, theair tube may serve as a guide support for insertion of the uninflatedmember 31 into the ear canal.

Assuming air tube 36 to be fully collapsible, probe 30 is deployed byfitting the ear mold or stop 34 into or against the patient's ear withthe collapsed member 31 directed inward. The inlet and outlet tubes 39and 41, respectively, are then connected to a suitable means forsupplying pressurized test fluid, such as, for example, closedcirculation pump such as that disclosed in U.S. Patent Application Ser.No. 762,437, by George Foti, filed Jan. 24, 1977, and entitled "PUMP FORCLOSED CIRCULATION SYSTEM". Such supply means is schematicallyillustrated at P in FIG. 10. When the pump is energized, water or othertest fluid under pressure is circulated through the balloon-like member31 through test fluid inflow and outflow conduits 39 and 41. The balloonexpands accordingly to conform to the contours of the patient's auditorycanal (B2). If a hermetic seal is provided by ear mold 34, which ispreferred the gradual expansion of member 31 requires the presence ofair tube 36 and recess 35 to prevent air which is trapped in the earfrom being pressurized and injuring the patient. Specifically, theexpanding member 31 forces trapped air out through the air tube 36 andbore 38. An indication of the expansion of member 31 is provided by thecontinued withdrawal of indicator 43 into bore 38. When member 31 isfully expanded the conical recess 35 prevents the end of the air tube36, which may be more rigid than the member 31, from being forced intopainful contact with the patient's ear drum. Test fluid may begin toflow out through outflow tube 41 upon full expansion of member 31, andcirculation of test fluid in member 31 then continued to more positivelycause expansion of member 31. The thin material of member 31 effectsefficient thermal transfer between the test fluid and the auditorycanal.

It is important to note that the ear mold can be made in one size toprovide a uniform fit in the tragus of most adults. This permits astandardization of testing procedures since the depth of penetrationinto the ear by member 31 is likewise uniform due to the stop functionserved by the proximal end of the ear mold.

The primary differences between probe 10 of FIG. 1 and probe 30 of FIG.4 reside in the use of ear mold 34, the fact that the distal end 32 ofprobe 30 is not contoured to the tympanic membrane, and the absence ofvanes 24 and 25. The transfer of thermal energy from probe 30 to areasof the auditory canal other than directly to the tympanic membrane issufficient to induce nystagmus response without contouring the distalend to the tympanic membrane, although some touching of the tympanicmembrane is preferable. The circulation within member 31, as forced byflow into inlet 39 and out of outlet 41, is sufficient without the needfor vanes 24 and 25.

Typical dimensions for probe 30, for use with adult patients, are asfollows: (a) the length A' from the proximal end 50 of ear mold 34 tothe distal end 32 of member 31 (expanded) is 24.5 mm; (b) the diameterB' of member 31 expanded is 6 to 6.5 mm; (c) air tube 36 has an innerdiameter of 0.25 mm and an outer diameter of 0.47 mm; (d) indicator 43is attached approximately 1 to 3 mm from the tip of end 32 and has anouter diameter of 0.1 mm; (e) the length of ear mold 34 is 14 mm and thediameter C' at the proximal end 50 of the ear mold is 15 mm; and (f) thedepth of the concavity in ear mold 34 is 4 mm. The thickness of thematerial comprising member 31 is on the order of 0.025 to 0.125 mm. Thedistal end of the air tube 36 begins approximately 2.5 mm from forwardend 32 of member 31; that is, the axial length of recess 35 isapproximately 2.5 mm. Indicator 43 is secured proximate this transitionbetween the recess 35 and tube 36. It is to be understood that thesedimensions are only examples of a specific embodiment and are notintended to limit the scope of the invention. Of course, allmeasurements must be scaled accordingly for use with adolescents,children and infants.

Although the technique described above for inserting the probe into apatient's ear assumes that member 31 is initially collapsed and theninflated after insertion, it should be noted that insertion may beeffected when member 31 is partially or fully inflated. Under suchcircumstances air tube 36 still serves the function of permittingtrapped air to egress from the ear canal as the canal is sealed by theexpanded member 31 and ear mold 34. The inner surface of the patient'sear canal may be coated with an appropriate lubricant to facilitatesliding the probe along the ear canal during either insertion technique.

A modification 30' of probe 30 is shown in FIGS. 6 and 7 wherein allparts are designated with the reference numerals associated withcorresponding parts in FIGS. 4 and 5. The modification in probe 30'comprises three additional conical recesses 44, 45 and 46 formed indistal end 32 of member 31. These recesses are equally spaced 120° apartabout recess 35 as a center. Air tubes 47, 48 and 49 communicate withand extend from recesses 44, 45 and 46, respectively, to a commonintersection point in air tube 36, which intersection point is typicallyspaced a distance K from the tip of end 32 of approximately 3 to 6 mm.The total of four ports in probe 30' further facilitates the egress oftrapped air from the ear canal during insertion.

Still another embodiment of the invention is illustrated as probe 50 inFIGS. 8 and 9. Probe 50 differs from probe 30 only in that the air tube36 and the cylindrical portion of member 31 between ends 32 and 33 isaccordion-pleated or corrugated. The corrugation facilitates storage ofmember 31, when collapsed, into the concave region of ear mold 34; inaddition, the corrugation strengthens member 31 against rupture when itis inflated. In the state illustrated in FIG. 8 member 31 is onlypartially expanded. When fully expanded the corrugations are completelyflattened and member 31 assumes the configuration of probe 30illustrated in FIG. 4. The corrugations in air tube 36 preferably remainfolded slightly (although in stretched form) in the full expansion stateof member 31 to provide additional strength against pressure build-upinside member 31.

A further embodiment 60 of the present invention is illustrated in FIG.10. In this embodiment the only difference from probe of FIG. 4 is thatair tube 36 is corrugated for the reasons discussed above. It should benoted that the four-inlet embodiment of FIG. 6 may be readily combinedwith the accordion-pleat feature of FIGS. 8 and 10.

The probe as described herein provides a simple, efficient and mess-freetechnique for applying caloric stimulus to the ear to produce nystagmus.The probe may be made to be disposable or re-usable, and is readilyusable with existing test fluid supplies and nystagmus measurementapparatus. Although described as being generally cylindrical and havingother specific configurations, it is to be understood that the shape ofthe probe is limited only in that it must fit in a patient's ear in amanner so that thermal transfer is efficiently achieved.

Likewise, it should be understood that a primarily important aspect ofthe probe is its ability to permit efficient thermal transfer betweenthe ear canal and drum and the test fluid. In this regard, in probe 10the material at end 12 (which end abuts the tympanic membrane) maydiffer from the material of the rest of the probe. For example, a thinsheet of thermally-conductive metal or a plastic impregnated with suchmetal may be used at end 12. I prefer, however, that the entire body bemade of the same thin material since efficient thermal transfercharacteristics are present in many types of polyurethanes and siliconeelastomers when in suitably thin sheet form. Moreover, using a singlematerial facilitates fabrication which may be by inexpensive injectionmolding techniques.

It should also be noted that a two-piece hinged ear mold may be used inconjunction with probe 10 of FIG. 1 or in place of ear mold 34. Such anear mold would be contoured to fit the external anatomy and would beprovided with bores necessary to permit the inlet and outlet tubes (andair tube) to pass through the mold.

The probes of the present invention may be used in numerous instances.For example:

(a) Evaluation of brain stem integrity of a comatose patient;

(b) Nystagmus inducing in comatose patient having basal skull fractureand concomittant cerebro-spinal otorrhea where open irrigation is notfeasible because of possible meningeal contamination;

(c) Initial screening of vertiginous patient by internists andneurologists, particularly when performed in conjunction with the Fotipump described in the aforementioned patent application by George Foti;

(d) Sophisticated electro-nystagmus analysis;

(e) Nystagmus inducing whenever a perforation of the tympanic membraneis suspected, thereby precluding open irrigation of the ear canal.

An important advantage of the probe of the present invention resides inthe fact that it conserves water and energy in comparison to priorcaloric test procedures. Specifically, rather than having to heat largevolumes of water, all of which is spilled over during conventional openflow caloric tests, the present probe uses a small volume of liquidwhich is continuously recycled through the probe. That liquid, onceheated, requires only slight re-heating as it recirculates.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to without departing from the true spirit and scope of theinvention as defined in the appended claims. It would be, moreover,readily apparent to one skilled in the art that the structure embodyingthe invention could be used to carry out medical procedures in a bodycavity other than the ear canal.

I claim:
 1. The method of caloric vestibular testing comprising:(a)inserting a flexible, thin-walled, distensible receptacle into an earcanal, the receptacle having provision for enabling circulation ofpressurized calorized fluid therethrough and being inflatable by suchfluid; (b) admitting pressurized calorized fluid into the receptacle tocause its expansion laterally within the ear canal and longitudinally upto the tympanic membrane, such expansion filling the cross sectionalarea of at least a portion of the ear canal; (c) while inflating thereceptacle, venting air trapped between the receptacle and the tympanicmembrane to atmosphere; and (d) circulating a volume of calorized fluidthrough the receptacle for a time period and at a temperature consistentwith and while carrying out a caloric vestibular function testingprocedure.
 2. The method according to claim 1, including visuallymonitoring the degree of longitudinal expansion of the receptacle whileit is being inflated by means of indicia located externally of the earcanal and moveable in direct relationship with longitudinal distensionof the receptacle.
 3. The method according to claim 1, wherein ventingof air is carried out through a flowpath provided by the structuralconfiguration of the receptacle and its associated structure.
 4. Themethod according to claim 1, wherein venting of air is carried outthrough a conduit extending longitudinally through the receptacle andisolated from the interior of said receptacle.